Until recently, pharmaceuticals, such as antibiotics, analgesics and hormones, derived from small organic molecules were mainly produced synthetically or in microbes. However, with the development of genomics and proteomics, new drug therapies involve larger protein molecules. Because proteins play key roles in cell biology and development, many proteins have therapeutic potential.
While short peptide chains of about thirty amino acids can be synthesized, larger proteins are best produced by living cells. Presently, a vast array of large proteins are produced using sterile microbial and mammalian cell cultures. However, because cell culture systems are expensive and laborious to maintain, plant-based expression systems provide lower production costs and more manageable large-scale production.